Stop using lists to represent args
This commit is contained in:
James Eversole
166
src/Eval.hs
166
src/Eval.hs
@ -2,63 +2,139 @@ module Eval where
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import Parser
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import Research
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import Data.Set (Set)
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import qualified Data.Set as Set
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import Data.List (foldl')
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import qualified Data.Map as Map
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import Data.Map (Map)
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import Data.Map (Map)
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evalSingle :: Map String T -> SaplingAST -> Map String T
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evalSingle env TLeaf = Map.insert "__result" Leaf env
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evalSingle env (TStem t) =
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let result = Stem (evalTreeCalculus env t)
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in Map.insert "__result" result env
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evalSingle env (TFork t1 t2) =
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let result = Fork (evalTreeCalculus env t1) (evalTreeCalculus env t2)
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in Map.insert "__result" result env
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evalSingle env (SFunc name [] body) =
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let value = evalTreeCalculus env body
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in Map.insert name value env
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evalSingle env (SVar name) =
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case Map.lookup name env of
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Just value -> Map.insert "__result" value env
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Nothing -> error $ "Variable " ++ name ++ " not defined"
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evalSingle env ast = Map.insert "__result" (evalTreeCalculus env ast) env
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evalSingle :: Map.Map String T -> SaplingAST -> Map.Map String T
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evalSingle env term = case term of
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SFunc name [] body ->
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let result = evalAST env body
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in Map.insert name result env
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SApp func arg ->
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let result = apply (evalAST env func) (evalAST env arg)
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in Map.insert "__result" result env
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SVar name -> case Map.lookup name env of
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Just value -> Map.insert "__result" value env
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Nothing -> error $ "Variable " ++ name ++ " not defined"
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_ ->
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let result = evalAST env term
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in Map.insert "__result" result env
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evalSapling :: Map String T -> [SaplingAST] -> Map String T
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evalSapling env [] = env
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evalSapling env [lastLine] =
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let updatedEnv = evalSingle env lastLine
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let
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lastLineNoLambda = eliminateLambda lastLine
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updatedEnv = evalSingle env lastLineNoLambda
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in Map.insert "__result" (result updatedEnv) updatedEnv
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evalSapling env (line:rest) =
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let updatedEnv = evalSingle env line
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let
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lineNoLambda = eliminateLambda line
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updatedEnv = evalSingle env lineNoLambda
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in evalSapling updatedEnv rest
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evalTreeCalculus :: Map.Map String T -> SaplingAST -> T
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evalTreeCalculus _ TLeaf = Leaf
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evalTreeCalculus env (TStem t) = Stem (evalTreeCalculus env t)
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evalTreeCalculus env (TFork t1 t2) = Fork (evalTreeCalculus env t1) (evalTreeCalculus env t2)
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evalTreeCalculus env (SApp base []) = evalTreeCalculus env base
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evalTreeCalculus env (SApp base args) =
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let func = evalTreeCalculus env base
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argVals = map (evalTreeCalculus env) args
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in foldl apply func argVals
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evalTreeCalculus env (SVar name) =
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case Map.lookup name env of
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Just value -> value
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Nothing -> error $ "Variable " ++ name ++ " not defined"
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evalTreeCalculus _ (SStr str) = toString str
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evalTreeCalculus _ (SInt num) = toNumber num
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evalTreeCalculus _ (SList elems) = toList (map (evalTreeCalculus Map.empty) elems)
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evalTreeCalculus _ (SFunc name args body) =
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error $ "Unexpected function definition " ++ name ++ " in \
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\ evalTreeCalculus; functions should be evaluated to Tree Calculus \
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\ terms by evalSingle."
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evalAST :: Map String T -> SaplingAST -> T
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evalAST env term = case term of
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SVar name ->
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case Map.lookup name env of
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Just value -> value
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Nothing -> error $ "Variable " ++ name ++ " not defined"
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TLeaf -> Leaf
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TStem t ->
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Stem (evalAST env t)
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TFork t1 t2 ->
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Fork (evalAST env t1) (evalAST env t2)
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SApp t1 t2 ->
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apply (evalAST env t1) (evalAST env t2)
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SStr str -> toString str
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SInt num -> toNumber num
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SList elems -> toList (map (evalAST Map.empty) elems)
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SFunc name args body ->
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error $ "Unexpected function definition " ++ name
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++ " in evalAST; define via evalSingle."
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SLambda {} ->
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error "Internal error: SLambda found in evalAST after elimination."
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result :: Map String T -> T
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result r = case (Map.lookup "__result" r) of
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Just a -> a
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Nothing -> error "No __result field found in provided environment"
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result r = case Map.lookup "__result" r of
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Just a -> a
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Nothing -> error "No __result field found in provided environment"
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eliminateLambda :: SaplingAST -> SaplingAST
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eliminateLambda (SLambda (v:vs) body)
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| null vs = lambdaToT v (eliminateLambda body)
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| otherwise =
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eliminateLambda (SLambda [v] (SLambda vs body))
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eliminateLambda (SApp f arg) =
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SApp (eliminateLambda f) (eliminateLambda arg)
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eliminateLambda (TStem t) =
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TStem (eliminateLambda t)
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eliminateLambda (TFork l r) =
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TFork (eliminateLambda l) (eliminateLambda r)
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eliminateLambda (SList xs) =
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SList (map eliminateLambda xs)
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eliminateLambda (SFunc n vs b) =
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SFunc n vs (eliminateLambda b)
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eliminateLambda other = other
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lambdaToT :: String -> SaplingAST -> SaplingAST
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lambdaToT x (SVar y)
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| x == y = tI
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lambdaToT x (SVar y)
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| x /= y =
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SApp tK (SVar y)
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lambdaToT x t
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| not (isFree x t) =
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SApp tK t
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lambdaToT x (SApp n u)
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| not (isFree x (SApp n u)) =
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SApp tK (SApp (eliminateLambda n) (eliminateLambda u))
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lambdaToT x (SApp n u) =
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SApp
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(SApp tS (lambdaToT x (eliminateLambda n)))
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(lambdaToT x (eliminateLambda u))
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lambdaToT x (SApp f args) = lambdaToT x f
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lambdaToT x body
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| not (isFree x body) =
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SApp tK body
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| otherwise =
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SApp
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(SApp tS (lambdaToT x body))
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tLeaf
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tLeaf :: SaplingAST
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tLeaf = TLeaf
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freeVars :: SaplingAST -> Set String
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freeVars (SVar v) = Set.singleton v
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freeVars (SInt _) = Set.empty
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freeVars (SStr _) = Set.empty
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freeVars (SList xs) = foldMap freeVars xs
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freeVars (SFunc _ _ b) = freeVars b
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freeVars (SApp f arg) = freeVars f <> freeVars arg
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freeVars TLeaf = Set.empty
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freeVars (TStem t) = freeVars t
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freeVars (TFork l r) = freeVars l <> freeVars r
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freeVars (SLambda vs b) = foldr Set.delete (freeVars b) vs
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isFree :: String -> SaplingAST -> Bool
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isFree x = Set.member x . freeVars
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toAST :: T -> SaplingAST
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toAST Leaf = TLeaf
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toAST (Stem a) = TStem (toAST a)
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toAST Leaf = TLeaf
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toAST (Stem a) = TStem (toAST a)
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toAST (Fork a b) = TFork (toAST a) (toAST b)
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tI :: SaplingAST
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tI = toAST _I
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tK :: SaplingAST
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tK = toAST _K
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tS :: SaplingAST
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tS = toAST _S
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